The fine thread-like structure found inside the nucleus is called nuclear reticulum or chromatin fibers. The unit of chromatin is the nucleosome. A necklace-like structure formed by enclosing histone proteins is called a nucleosome. Each human cell contains about 3×107 nucleosomes. It is called chromatin because it contains some basic color (fluorescent color) when the cell is stained. Chromatin is characterized by two regions due to its ability to absorb color. Euchromatin and Heterochromatin. The darker colored denser region of chromatin is called heterochromatin and the lighter colored less dense region is called euchromatin. Chromatin is divided into thick and short sections called chromosomes. Each chromatin contains DNA, histone proteins and non-histone proteins.
Function: Chromatin contains DNA. It acts as a carrier and carrier of hereditary characteristics. It plays a key role in the variation and mutation of organisms.